How it should have ended...
Before Dark Fate was released, they should have re-released this with an update.
Arnie's T800 turns to John and Sarah and informs them that to make sure that Skynet never comes into existence, he must sacrifice himself by lowering himself into the vat of molten metal.
John Connor cries out in anguish, having bonded with his protector over the course of their high-adrenaline chase and adventure. Sarah Connor clutches her son. She gives the T800 a grudgingly nod to thank him for all that this cyborg has done for humanity and for being a protective father-figure to her son..
The T800 lowers himself into the molten metal. As he starts to dissolve, he gives them a thumbs up, a sign of their mutual victory over the T1000 and the dark future he came from... a dark future that will no longer exist thanks to their efforts.
Credits roll... and then there is a post-credit scene...
John and Sarah are enjoying themselves three years later at a beach in Mexico. Suddenly, ANOTHER T800 walks out of the crowd, pulling out a handgun. BLAM-BLAM-BLAM!
Sarah screams as bullets rip into her son. He falls to the ground, clearly dead.
The T800 drops the gun, turns and walks away...
I think this movie would have been so much better if they had tacked on the opening from DF. Then DF could simply have started its story in our present just as it does.